The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Existing Earth Leakage Circuit Breaker (ECLB) systems are divided into two types: 1) voltage operated ELCB (vELCB) and 2) current operated ELCB (iELCB). As the name implies, a vELCB operates based on the electrical potential difference (voltage) between the monitored grounding terminal/metal part and a locally Earthed conductor. vELCB acts to break a circuit when the detected voltage reaches or goes beyond a predetermined limit. Because essentially no current is involved with a vELCB detection system, the major advantage of the vELCB is that the devices are able to detect a ground fault with a negligible leakage current. The biggest disadvantage for vELCB detection systems is the necessity of having a functional Earth connection. By “functional Earth connection” it is meant a conductor that is physically connected to Earth.
The second major type of ELCB detection system, an iECLB system, is often referred to in North America as “Ground Fault Circuit Interrupter” (GFCI) system. An iECLB operates by measuring the sum of current flowing into and out of an electrical device. In normal operation this sum will be zero, which means there is no current leakage in the system. Put differently, the current flowing into a device is equal to the current flowing out of the device. An iELCB detection system operates by detecting when the magnitude of current flowing into some device on a hot line of an AC power source becomes different from the current flowing on the neutral line of the power source (i.e., the sum of current flowing into and out becomes “non-zero”). When this non-zero current reaches a predetermined upper limit, then an iELCB detection system trips a breaker to interrupt current flow to the component or device. A principal advantage of an iELCB detection system is that no real Earth connection is required. However, a principal drawback, at least in some industries and/applications, is that there needs to be some tangible level of current flow to component or device that is coupled to the AC power source, in order to be able to detect if there exists a predetermined magnitude of difference in the current flowing to the device and the current leaving the device.
One specific application where an ELCB system is required is in connection with Electric Vehicle Supply Equipment (EVSE) used to recharge the batteries of an electric vehicle. Safety standards associated with EVSE equipment require that such equipment must continually monitor a protective Earth (PE) connection and interrupt the power to the electric vehicle if a PE connection fails. Two specific International Electrotechnical Commission (IEC) standards require that the power outlet PE terminal (i.e., receiving power from an AC power source) shall not be connected with the vehicle PE terminal until the power outlet PE grounding is verified. But with an electric vehicle, the vehicle itself does not present a direct, conductive ground path to the Earth (i.e., a PE connection). And still, IEC standards do not allow power to be coupled to the vehicle until a proper PE connection is verified, so an iELCB detection system cannot be used because no tangible current flow is permitted to be passed to the vehicle with first verifying the PE connection.